Ru-based donor-acceptor photosensitizer that retards charge recombination in a p-type dye-sensitized solar cellBased on the presentation at Dalton Discussion No. 13, 10-12 September 2012, University of Sheffield, UK.Electronic supplementary information (ESI) available. See DOI: 10.1039/c2dt30829k

We report on the synthesis and characterization of a donor-acceptor ruthenium polypyridyl complex as a photosensitizer for p-type dye-sensitized solar cells (DSSCs). The electrochemical, photophysical, and photovoltaic performance of two ruthenium-based photosensitizers were tested in NiO-based DSSCs; bis-(2,2′-bipyridine-4,4′-dicarboxylic acid) 2 N -(1,10-phenanthroline)-4-nitronaphthalene-1,8-dicarboximide ruthenium( ii ), ([Ru(dcb) 2 (NMI-phen)](PF 6 ) 2 ) and tris-(2,2′-bipyridine-4,4′-dicarboxylic acid) 3 ruthenium( ii ), [(Ru(dcb) 3 )Cl 2 ]. The presence of an electron-accepting group, 4-nitronaphthalene-1,8-dicarboximide (NMI), attached to the phenanthroline of [Ru(dcb) 2 (NMI-phen)] 2+ resulted in long-lived charge separation between reduced [Ru(dcb) 2 (NMI-phen)] 2+ and NiO valence band holes; 10-50 μs. In the reduced state for [Ru(dcb) 2 (NMI-phen)] 2+ , the electron localized on the distal NMI group. In tests with I 3 − /I − and Co(4,4′-di- tert -butyl-bipyridine) 3 2+/3+ electrolytes, [Ru(dcb) 2 (NMI-phen)] 2+ outperformed [Ru(dcb) 3 ] 2+ in solar cell efficiency in devices. A record APCE (25%) was achieved for a ruthenium photosensitizer in a p-type DSSC. Insights on photosensitizer regeneration kinetics are included. Enhanced charge separation and regeneration by the use of a Ru-acceptor dye in a NiO-based p-type dye-sensitized solar cell.